"Hobson and McCarley originally proposed in the 1970s that the differences in the waking-NREM-REM sleep cycle was the result of interactions between aminergic REM-off cells and cholinergic REM-on cells.[4] This was perceived as the activation-synthesis model, stating that brain activation during REM sleep results in synthesis of dream creation.[1][1] Hobson's five cardinal characteristics include: intense emotions, illogical content, apparent sensory impressions, uncritical acceptance of dream events, and difficulty in being remembered."

Claude Shannon: "Communication in the Presence of Noise"
File:Shannon noise.pdf
"We will call a system that transmits without errors at the rate C an ideal system.
Such a system cannot be achieved with any finite encoding process
but can be approximated as closely as desired."